Pessimistic locking a record or page get locked immediately - Database

Discussion

• Nirja Shah   -Posted on 03 Nov 15
  - A lock, as a read lock or write lock, is used when multiple users need to access a database concurrently.
  
  - It prevents the data from being corrupted or invalidated when multiple users try to read while others write to the database.
  
  - There are two mechanisms for locking data in a database: pessimistic locking, and optimistic locking.
  
  Pessimistic locking
  - It is a record or page that is locked immediately when the lock is requested.
  
  Optimistic lock
  - The record or page which is only locked when the changes made to that record are updated.
  
  - The latter situation will be appropriate only when there is less chance of someone needing to access the record while it is locked; otherwise it cannot be certain that the update will succeed because the attempt to update the record will fail if another user updates the record first.
  
  - With pessimistic locking it is guaranteed that the record will be updated.

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